The present invention generally relates to material ablation with pulsed light sources and particularly relates to laser drilling and laser milling.
Material ablation by pulsed light sources has been studied since the invention of the laser. Reports in 1982 of polymers having been etched by ultraviolet (UV) excimer laser radiation stimulated widespread investigations of the process for micromachining. Since then, scientific and industrial research in this field has proliferatedxe2x80x94mostly spurred by the remarkably small features that can be drilled, milled, and replicated through the use of lasers.
Ultrafast lasers generate intense laser pulses with durations from roughly 10xe2x88x9211 seconds (10 picoseconds) to 10xe2x88x9214 seconds (10 femtoseconds). Short pulse lasers generate intense laser pulses with durations from roughly 10xe2x88x9210 seconds (100 picoseconds) to 10xe2x88x9211 seconds (10 picoseconds). A wide variety of potential applications for ultrafast lasers in medicine, chemistry, and communications are being developed and implemented. These lasers are also a useful tool for milling or drilling holes in a wide range of materials. Hole sizes as small as a few microns, even sub-microns, can readily be drilled. High aspect ratio holes can be drilled in hard materials, such as cooling channels in turbine blades, nozzles in ink-jet printers, or via holes in printed circuit boards.
The ability to drill holes as small as microns in diameter is a basic requirement in many high-tech manufacturing industries. The combination of high resolution, accuracy, speed, and flexibility has allowed laser processing to gain acceptance in many industries, including the (manufacture of integrated circuits, hard disks, printing devices, displays, interconnects, and telecommunication devices.
Hole shape is critical to the individual manufacturing application. Laser systems are more flexible to use in milling because appropriate programming can easily engineer custom-designed and tapered two-dimensional (2D) and three-dimensional (3D) structures. However, as the required feature size for these structures decreases, mass production of micromachined products becomes more difficult to conduct in a rapid, cost-effective manner that consistently meets product specifications. The need remains, however, for a method of laser milling that solves several problems that continue to exist in the field of material ablation with pulse light sources.
One problem that continues to exist in the field of material ablation with pulse light sources relates to milling holes of varying shapes that require controlled taper angles. Current market applications for precision milled materials require a variety of shapes and taper angles. Technologies used in the past to remove (or ablate) workpiece materials include electric discharge machining (EDM) and excimer lasers with masking. However, such methods require extensive set-up and development times to mill varying materials and taper angles. What is needed is a way to mill holes of varying shapes that require controlled taper angles.
Another problem that continues to exist in the field of material ablation with pulse light sources relates to milling holes in a variety of materials with varying material thicknesses. Excimer lasers are currently used for milling holes; however, they are primarily used on polymeric materials and are not versatile due to requirements for masking. The current market for micromachining encompasses a wide variety of materials and applications. What is needed is a way to mill holes in a variety of materials with varying material thicknesses.
Another problem that continues to exist in the field of material ablation with pulse light sources relates to milling geometrically repeatable holes using parallel processing. Conventional techniques for milling materials incorporate a single beam (such as an excimer laser) and a masking technique. Although these processes are effective for single-hole milling, they do not allow for multiple or parallel processing of more than one hole at a time. What is needed is a way to mill geometrically repeatable holes using parallel processing.
Another problem that continues to exist in the field of material ablation with pulse light sources relates to milling materials without requiring a masking process. Current methods of milling typical workpiece materials include such techniques as excimer laser milling. Excimer laser milling typically requires a masking material to be placed onto the workpiece surrounding the hole target area. The excimer laser ablates all the unmasked material on the workpiece. However, to form a tapered angle in the workpiece, a mask must be made for each individual layer of ablation. This technique is time consuming and generates excessive amounts of wasted energy. What is needed is a way to mill materials without requiring a masking process.
The present invention is a method of laser milling varied shape, geometrically repeatable holes where a laser drilling system is provided to ablate material. Desired hole geometry is determined based on customer specifications, ablation rate is determined using laser drilling system parameters, and a tool path algorithm is determined based on the geometry, ablation rate, and laser drilling system parameters. The laser milling method may be used in combination with single or parallel processing.
To simplify description of the laser milling process, the laser milling process according to the present invention is described with respect to making round hole shapes. It should be understood, however, that the present invention is not limited to round shapes only. Other shapes, such as rectangles and triangles can be milled using the same process described herein. Moreover, it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.